Cyclohexa-1,4-diene

1,4-Cyclohexadiene is an organic compound with the formula C6H8. It is a colourless, flammable liquid that is of academic interest as a prototype of a large class of related compounds called terpenoids, an examples being γ-terpinene. An isomer exists of this compound, 1,3-cyclohexadiene.

Cyclohexa-1,4-diene
1,4-Cyclohexadiene molecule
1,4-Cyclohexadiene molecule
Names
Systematic IUPAC name
Cyclohexa-1,4-diene[1]
Other names
1,4-Cyclohexadiene
1,4-Dihydrobenzene
Identifiers
CAS Number
3D model (JSmol)
Abbreviations 1,4-CHDN
Beilstein Reference
 1900733
ChEBI
ChemSpider
ECHA InfoCard 100.010.040
EC Number
  • 211-043-1
Gmelin Reference
 1656
MeSH 1,4-cyclohexadiene
PubChem CID
UNII
UN number 3295
CompTox Dashboard (EPA)
Properties
Chemical formula
 C6H8
Molar mass 80.130 g·mol−1
Appearance Colorless liquid
Density 0.847 g cm−3
Melting point −50 °C; −58 °F; 223 K
Boiling point 82 °C; 179 °F; 355 K
Magnetic susceptibility (χ)
 -48.7·10−6 cm3/mol
Refractive index (nD)
 1.472
Thermochemistry
Heat capacity (C)
 142.2 J K−1 mol−1
Std molar
entropy (So298)
 189.37 J K−1 mol−1
Std enthalpy of
formation (ΔfH⦵298)
 63.0-69.2 kJ mol−1
Std enthalpy of
combustion (ΔcH⦵298)
 -3573.5--3567.5 kJ mol−1
Hazards
GHS pictograms
GHS Signal word Danger
GHS hazard statements
 H225, H340, H350, H373
GHS precautionary statements
 P201, P210, P308+313
NFPA 704 (fire diamond)
3
2
0
Flash point −7 °C (19 °F; 266 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Synthesis and reactions

In the laboratory, substituted 1,4-cyclohexadienes are synthesized by Birch reduction of related aromatic compounds using an alkali metal and a proton donor such as ammonia. In this way, over reduction to the fully saturated ring is avoided.

1,4-Cyclohexadiene and its derivatives are easily aromatized, the driving force being the formation of an aromatic ring. The conversion to an aromatic system may be used to trigger other reactions, such as the Bergman cyclization.[2]

References
  1. "1,4-cyclohexadiene - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 27 March 2005. Identification and Related Records. Retrieved 12 October 2011.
  2. John C. Walton, Fernando Portela-Cubillo "1,4-Cyclohexadiene" Encyclopedia of Reagents for Organic Synthesis 2007 John Wiley & Sons. doi:10.1002/047084289X.rn00806
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